The pressing of the grapes is generally carried out in several grape-pressurizing cycles, each cycle being followed by a marc-crumbling operation, or toeing-up, inside the wine press.
By way of an example, in the particular field of the production of champagne, the pressing includes a first slow pressure-raising step that allows achieving the cuvée that represents a quantity of 20.5 hl for 4,000 kg of grapes, then, after a crumbling, a second operation consisting of one or several more important pressings, each followed by a crumbling, providing the taille representing 5 hl, also for 4,000 kg of grapes.
The wine presses are traditionally vertical, they are however progressively replaced by the horizontal wine presses.
The vertical wine presses include a receptacle in which are placed the grapes, and pressing means actuated vertically, through a screw or a jack, capable of compressing the grapes in said receptacle. In these vertical wine presses, the crumbling is performed manually, by means of spades and forks.
The horizontal wine presses are mainly of two types, with a membrane or with pistons. They include a cylindrical basket for receiving the grapes, in which acts either an axially arranged inflatable membrane capable of compressing the grapes against the wall of said basket, or a circular or rectangular tray, movable in axial translation, capable of crushing the grapes against a wall, or two circular or rectangular trays movable towards each other. In these wine presses, the crumbling of the marc cake is carried out through rotation of the basket, after removal of the pressing means, i.e. deflating of the membrane or drawing back of the tray or trays.
The horizontal wine presses have been implemented in order to facilitate the crumbling and the emptying operations and to limit the manual interventions; they do however have drawbacks when performing these operations.
The pressure exerted during the pressing is indeed such that, despite the movement of the basket, the marc can remain agglomerated against the wall of the latter, so that the crumbling and the emptying of the marc requires nonetheless manual interventions.